The broad objective of this research is to comprehensively characterize the structure, growth and maturation of Staphylococcus aureus biofilms as well as the phenotypic similarities and differences between staphylococci grown as biofilm versus planktonic cells. In particular, we will probe the adhesion properties of both mature biofilms and planktonic cells since they are critical to both biofilm initiation and immune system response. Elucidation of these phenotypic differences may ultimately lead to the design of novel therapeutic strategies for staphylococcal biofilm prevention and control. We hypothesize that the repertoire and number of surface expressed S. aureus proteins vary depending on the mode of growth. We further hypothesize that this variance will directly affect the adhesion properties of both the biofilm and detached planktonic bacteria under shear conditions. The specific aims of the project are to (1) investigate the architecture of staphylococcal biofilms grown on protein surfaces in the presence and absence of serum under controlled shear conditions, including growth and developmental characteristics, (2) characterize adhesion properties of staphylococcal biofilms and detached planktonic cells grown in the presence and absence of serum as a function of wall shear stress and (3) characterize the intracellular, membrane-bound and secreted protein expression patterns as a function of how staphylococci are grown. Suspension cultures at various growth stages, surface-attached cells in various stages of biofilm development, and planktonic populations shed from biofilms will be evaluated and compared. Completion of these specific aims will provide a rational basis for the design of new therapeutic molecules.